The Fibroblast Growth Factor (FGF) family is a superfamily of growth factors containing at least 23 members, many of which are potent regulators of cell proliferation, differentiation and cell function. All of the FGFs have a conserved 120 amino acid core. Members of the family share conserved cysteine residues and 30-50% sequence homology at the amino acid level. The molecular weight of the FGFs ranges from 7 kDa for FGF-1 to 38 kDa for FGF-5. The length of the proteins is from 60 amino acids in the case of an FGF-1 splice variant to 288 amino acids for FGF-2. Binding to heparin is an essential step required for an FGF factor to interact with cell surface receptors.
FGF5 is a secreted signaling protein consisting of 268 amino acids with a 17 amino acid signal sequence and a 251 amino acid mature peptide. The human gene also gives rise to a glycosylated alternate splice form that is 18 kDa in size and 123 amino acid in length. The murine homologue of FGF-5 was cloned and found to be 84% homologous to the human protein at the amino acid sequence level. Human FGF-5 consists of three exons and maps to chromosome 4q21 and cross-reacts with murine FGF-5.
Formation of hair follicles involves a complex series of steps: growth (anagen), regression (catagen), rest (telogen) and shedding (exogen). FGF-5 has been implicated as one of the major drivers of the transition from anagen to catagen in the hair cycle. Expression of FGF-5 is detected in hair follicles from wild-type mice and is localized to the outer root sheath during the anagen phase. Mice homozygous for a predicted null allele of FGF-5, fgf5neo, have abnormally long hair (See, Hebert et al., Cell 78: 1017-25 [1994]). The phenotype appears identical to that of mice homozygous for the spontaneous mutation angora (go). Recently, partial FGF-5 sequences, FGF5S, thought to compete with FGF-5 in binding to the receptor have been identified, (See, Ito et al., J. Cell Physiol., 197:272-83 [2003]).
The Bowman-Birk protease inhibitor (BBI) is a designation of a family of stable, low molecular weight trypsin and chymotrypsin enzyme inhibitors found in soybeans and various other seeds, mainly leguminous seeds and vegetable materials. BBI comprises a family of disulfide bonded proteins with a molecular weight of about 8 kD (See e.g., Chou et al., Proc. Natl. Acad. Sci. USA 71:1748-1752 [1974]; Yavelow et al., Proc. Natl. Acad. Sci. USA 82:5395-5399 [1985]; and Yavelow et al., Cancer Res. (Suppl.) 43:2454s-2459s [1983]). BBI has a pseudo-symmetrical structure of two tricyclic domains each containing an independent native binding loop, the native loops containing binding sites for both trypsin and chymotrypsin (See, Liener, in Summerfield and Bunting (eds), Advances in Legume Science, Royal Bot. Gardens, Kew, England). These binding sites each have a canonical loop structure, which is a motif found in a variety of serine proteinase inhibitors (Bode and Huber, Eur. J. Biochem., 204:433-451 [1992]). Commonly, as in one of the soybean inhibitors, one of the native loops inhibits trypsin and the other inhibits chymotrypsin (See, Chen et al., J. Biol. Chem., 267:1990-1994 [1992]; Werner & Wemmer, Biochem., 31:999-1010 [1992]; Lin et al., Eur. J. Biochem., 212:549-555 [1993]; and Voss et al., Eur. J. Biochem., 242:122-131 [1996]) though in other organisms (e.g., Arabidopsis), both loops are specific for trypsin.
STI inhibits the proteolytic activity of trypsin by the formation of a stable stoichiometric complex (See e.g., Liu, Chemistry and Nutritional Value of Soybean Components, In: Soybeans, Chemistry, Technology and Utilization, pp. 32-35, Aspen Publishers, Inc., Gaithersburg, Md., [1999]). STI consists of 181 amino acid residues with two disulfide bridges and is roughly spherically shaped (See e.g., Song et al., J. Mol. Biol., 275:347-63 [1998]). The trypsin inhibitory loop lies within the first disulfide bridge. The Kunitz-type soybean trypsin inhibitor (STI) has played a key role in the early study of proteinases, having been used as the main substrate in the biochemical and kinetic work that led to the definition of the standard mechanism of action of proteinase inhibitors.
Eglin C is a small monomeric protein that belongs to the potato chymotrypsin inhibitor family of serine protease inhibitors. The proteins that belong to this family are usually small (60-90 amino acid residues in length) and contain no disulfide bonds. Eglin C, however, is highly resistant to denaturation by acidification or heat regardless of the lack of disulfide bonds to help stabilize its tertiary structure. The protein occurs naturally in the leech Hirudo medicinalis. 
Despite much research into hair growth and its modulation, a need remains for efficient and effective means to modulate hair growth as desired.